Continuously Variable Transmissions (CVTs) are classified into the following three large groups according to functionality: friction transmissions, free-wheel (i.e., coming and going or oscillatory) transmissions, and hydrostatic transmissions.
Friction transmissions are classified as toroidal and as variable pulley, and have at least two rotating bodies having one contact point among them. The rotating bodies have the same tangential velocity, where the transmission rotation varies by changing the effective contact radium of both elements. Some classical examples of friction transmissions are: the Van Doorne metallic belts, the chained Van Doorne, the toroidal shift, Torotrak transmissions, the Extroid transmission, the Milner transmission, and the ringed-cone transmission, with all of them generally being small-sized and used in automotive vehicles, machinery, and other small-sized and low torque equipment.
Free-wheel transmissions, or coming and going or oscillatory transmissions, are transmissions in which the rotation in an entrance axis provides a determined mechanism and converts into an oscillatory movement of variable amplitude. This movement of coming and going is rectified with a free wheel in order to obtain a unidirectional rotation movement in an exit axis. Using several mechanisms in parallel, it is possible to transmit continuously and minimize undulation of the exit angle, thus minimizing the torque oscillation in the exit axis. These transmissions are not commonly used in the automotive industry due to the difficulty of configuration and exit speed inconsistency and subsequent vibration due to the intermittent torque transmission. Some classic examples of free-wheel transmissions are: the Lestraneng transmission, the Varibox transmission, the continuously variable IVPD transmission, the Constantinesca transmission, and the Transrevolution transmission.
Hydrostatic transmissions transform rotational energy of an entrance axis in fluid flow in a pump and later convert this fluid flow into a rotating movement of an exit axis by means of a hydrostatic engine or turbine. In these transmissions, sometimes the flow is varied through the variable output pump and in other times the output is controlled by control valves. Thus, the transmission relation of the system obtains an infinite array of velocities. This type of transmission has the advantages of having big configurations, which are usually used in utility mechanisms, tractors, and heavy vehicles, but they are not applied to high rotations. Some classic examples of hydrostatic transmissions are those that apply a variable pump with axial pistons activated by an inclined disc with variable angular inclination.
There are some documents that describe continuously variable transmissions destined for several applications, although none of these transmissions have the configuration, application, and functions described in this disclosure. Among these documents, it is worth mentioning the following:
BRPI 0315187-5, titled CONTINUOUSLY VARIABLE TRANSMISSION, describes a continuously variable transmission for use with engine run vehicles. The continuously variable transmission includes an electronic control unit, an automatic gear shift unit, an inverter, a set of entrance gears, an element of fixed entrance relation, and an element of fixed exit. The electronic control unit is configured to include rules of logic to control the transmission. The rules of logic include emitting control commands of the transmission.
BRPI 0407856-0, titled CONTINUOUSLY VARIABLE TRANSMISSION, describes the invention of a variable velocity transmission that has a plurality of inclination spheres (1), entrance discs (34), and exits (101) opposed to each other, which provides an infinite number of velocity combinations per its relation of transmission. The use of a set of planetary gears enables minimum velocities in the inversion and the unique geometry of the transmission allows that all of the power courses are coaxial. This reduces the general size and complexity of the transmission, in comparison to transmissions that reach ranges of relations in similar transmissions.
BRPI 9301842-8, titled OUTPUT VARIATION DEVICE IN ROTATING PUMPS OF POSITIVE OR VARYING DISPLACEMENT OF ROTATION SPEED IN HYDRAULIC AND PNEUMATIC ENGINES, AND HYDROSTATIC VARIATION OF ROTATION SPEED, is constituted of all and any mechanical element or set of elements that has the property of varying the useful width “I” (3), of internal and external gears, lobes, lobes with tooth, friction wheels, cubes, picks, bolts, etc. The element(s) comprise a rotating pump and/or hydraulic rotating engine and/or pneumatic with the junction of the variation device of the output in rotating pumps, and the device of rotation variation in hydraulic rotating engines and pneumatic, forming the hydrostatic variation of rotation speed.
BRPI 9604066-1, titled GEARS PUMP WITH VARIABLE OUTPUT BY THE AXIAL DISPLACEMENT PRINCIPLE OF THE MOVED, REVERSIBLE GEARS IN HYDRAULIC ENGINE, provides the pumping of fluids at a variable output without the need to vary the rotation speed of the starter and without the need to obstruct the consolidation output and the recirculation of the exceeding output to the suction pump, thereby saving fuel and rationalizing the controls of the hydraulic circuits. This principle consists in varying the positions of gears (“useful width”) between the external teeth driver gears (4) and the driver gear (9), varying the volume pumped at each revolution. The driver gear (4) does not have longitudinal movement. When they are not geared, the opposite extremities from each other of the gears have empty spaces between the teeth, occupied by the internally teethed gears (3) and (10), preventing the internal recirculation of the fluid. The increase of the useful width is obtained by means of the internal hydrostatic forces; the decrease is obtained by the movement of the axis (8) and the journal bearing (2). Cooperation between them dislocates axially from left to right taking the internal teeth gears (3) and the moved gear (9) in the same direction. The internal teeth gear (10) does not move in the axial direction. The triggering of the mobile parts in the axial direction is obtained by means of hydraulic command using its own pumped fluid, recirculating it until the command mouth (15), or obtained by means of external mechanisms. The gear pump of variable output is reversible, with the possibility of being used as a hydraulic engine of variable rotation speed. In this case there is a constant output of fluid destined to transmit power to the axis of the mentioned hydraulic engine, being that the axis has its variable rotation speed due to the internal useful width of the engine, obtained by the same principle of gear pumps at variable output.
There are some other documents that can be cited like WO 2006049500, EP 0478514, EP 1991 0830381, U.S. Pat. No. 7,137,798, and U.S. Pat. No. 7,153,110.